1. Field of the Invention
The present invention generally relates to a process of recovering fine coal and more particularly to a process which enables recovery of fine coal having a size at or below 400 mesh. The process includes a series of cyclone separators, a vibrating screen, a centrifuge and a flow path to clean, recover and dewater fine coal having a nominal size of 3 mm down to 400 mesh or below. The process includes the use of commercially available components arranged to efficiently recover fine coal for use in various energy supplying systems.
2. Description of the Prior Art
Prior art in this field of endeavor utilizes various types of separators to separate fine coal from contaminants which utilizes cyclones, vibrating screens and centrifuges by which fine coal can be cleaned and recovered for use in various energy producing systems. However, the prior art recovery systems for fine coal do not include the specific interrelationships between the components of the recovery process as utilized in the present invention.
The process for recovering fine coal of the present invention includes a raw coal sump which provides a supply of raw coal, contaminants and a liquid, such as water, to form a slurry which is pumped into a bank of cyclones such as water only cyclones. The underflow from the water only cyclones discharges to a column cell sump and the overflow from the water only cyclones is discharged to a classifying cyclone sump. The material in the classifying cyclone sump is pumped to a bank of classifying cyclones for sizing.
The classifying cyclone underflow, clean coal, is deposited onto a high frequency vibrating screen which provides initial dewatering of the clean coal. The classifying cyclone overflow also discharges to the column cell sump. The material in the column cell sump which includes the overflow from the water only cyclones and the classifying cyclones is pumped to column flotation cells for cleaning.
The float from the column flotation cells, clean coal, is discharged to a clarifying cyclone sump and the sink, or rejects, from the column flotation cells is discharged to waste. The material in the clarifying cyclone sump is pumped to clarifying cyclones to remove below 400 mesh material and the overflow from the clarifying cyclones, over 400 mesh, is discharged to waste.
The clarifying cyclones discharge underflow onto the bed of material on the high frequency vibrating screen formed by the material discharged onto the high frequency vibrating screen from the classifying cyclone underflow. The initial bed formed by the classifying cyclone underflow material will trap the material discharged onto the bed from the clarifying cyclones underflow.
Underflow from the high frequency vibrating screen is discharged to the clarifying cyclone sump and is recycled through the system and the overflow from the high frequency vibrating screen is discharged to a centrifuge for further dewatering. The effluent from the centrifuge is discharged to the clarifying cyclone sump and is recycled through the system and the dewatered clean fine coal product from the centrifuge is discharged to a conveyor and stockpiled as finished product.
Accordingly, an object of the present invention is to provide a process for recovering fine coal utilizing a serial arrangement of water only cyclones, classifying cyclones, clarifying cyclones, a vibrating screen and a centrifuge for depositing cleaned fine coal in a stockpile for subsequent use and discharging contaminants or the like above 400 mesh size from the clarifying cyclones and column flotation cells to waste. The underflow from the vibrating screen and the effluent from the centrifuge is recycled through the system by discharge into a clarifying cyclone sump. The clarifying cyclone sump also receives material from the column flotation cells. The column float cells discharges contaminant material to waste and the separated material is discharged into the clarifying cyclone sump for recycling through the system.
Another object of the invention is to provide a fine coal recovering process which enable efficient recovery of fine coal at or below 400 mesh in size which includes a series of cyclone separators, a vibrating screen and a centrifuge dewatering device to produce cleaned, dewatered fine coal to a stockpile or other storage area combined with a column cell arrangement and a flow path which enables recycling of a portion of the material which passes through the cyclones, vibrating screen and centrifuge back through the system for more effective complete separation of fine coal from contaminants that are discharged to waste.